This invention relates to apparatus for disintegrating bales of wood pulp sheets into their constituent cellulosic fibers. This kind of apparatus is also known as a fluff generator. The fibers agglomerate to form a fluffy mass which is used as a fluid absorbent layer in such body worn articles as disposable sanitary napkins and diapers.
The invention disclosed herein is an improved version of a fluff generator that is described in U.S. Pat. No. 3,967,785 which issued to G. S. Grosch and is assigned to Curt G. Joa, Inc., as is the interest of one of the joint inventors in the present application. U.S. Pat. No. 3,967,785 is incorporated herein by reference.
The cited patent discloses a fluff generator comprised of a circular stationary horizontal bed plate. The plate has an elongated opening or port in it. The port extends radially on both sides of the bed plate center. There is a shaft journaled for rotation about a horizontal axis below the bed plate in parallelism with the port. The shaft carries a generally cylindrical cutting mill constituted by a plurality of blades that have cutting edges at the periphery. The cutting edges extend through the port sufficiently far to bite into the bottom pulp sheet in a stack or bale of such sheets that is on the bed plate and is rotated about a vertical axis to sweep it over the mill.
Above the bed plate there is a hollow cylinder or tub having an open top and bottom. The tub is supported on rollers about its lower rim and is power driven at nominal speed for causing it to rotate about a vertical axis. The tub has guide means in it for retaining a single pulp bale against lateral movement and for guiding the bale so it settles on the bed plate. The center of the usually square bale is coincident with the virtual vertical rotational axis of the tub. Thus, rotation of the tub over the bed plate causes the bottom sheet of the pulp bale to sweep over the cutting edges of the mill extending through the port to thereby disintegrate the pulp sheet or sheets at the bottom of the bale into fibers. In the patented apparatus, the axial length of the cutting mill is long enough to have it interface with the full distance from the center of the bale to a corner thereof, that is, the mill is long enough to reach over the diagonal or maximum dimension of the bale.
Although the patented design produced good results in practical applications, it was perceived to be subject to improvement. One of its weaknesses is that the bottom of the bale tends to cavitate or form a dish-shaped concavity during operation. The reason appears to be that the center part of the rotating bale was over the radially inner end of the mill for a greater length of time than the more radially outward perimeter and corners of the lower end of the bale. This cavitation phenomena resulted in something less than optimum output of fluff from the apparatus.